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RCA SB256 256-bit production Selectron
Selective Electrostatic Storage Tube
Tube à mémoire
Selectron 256-Bit Digitale Speicherröhre

The Selectron was an early form of digital computer memory developed by Jan A. Rajchman at RCA.

About 200 256-bit "production" tubes were produced in the early 1950s.

The AFCRC (Air Force Cambridge Research Center) Memory System, designed and built by the staff at RCA Laboratories in Princeton, used 20 SB256 Selectrons.

The JOHNNIAC (short for John v. Neumann Numerical Integrator and Automatic Computer) built by RAND in 1953 used 40 Selectrons for its fast access memory, but they were replaced by core memory in March 1955.

The magnetic-core memory, which emerged in 1953, sounded the death knell of the Selectron tube.

Everything you may want to know about the SELECTRON has been gathered by Charles S. Osborne on his website:
The RCA Selectron: A 1940s vacuum tube digital memory

Picture of the Johnniac under construction with Selectron tubes:
Computer History Museum

Fiche technique • Data sheet • Datenblatt: SB256.pdf

 

RCA SB256 SELECTRON

Hauteur • Height • Höhe : 240 mm • 9" 4/10
Diamètre • Diameter • Durchmesser : 76 mm • 3"
Poids • Weight • Gewicht : 860 g • 1.90 lbs

RCA SB256 SELECTRON

The number P990-4 is manually etched on the bulb

RCA SB256 SELECTRON

RCA SB256 SELECTRON

From US Patent 2,604,606 (Filed Oct. 15, 1949)

RCA SB256 SELECTRON

From Max Knoll and Benjamin Kazan, Storage Tubes and Their Basic Principles, 1952

RCA SB256 SELECTRON

RCA SB256 SELECTRON

RCA SB256 SELECTRON

RCA SB256 SELECTRON

RCA SB256 SELECTRON

RCA SB256 SELECTRON

RCA SB256 SELECTRON

Magnetic-Core Memory (detail)

Magnetic-Core Memory (detail)

 


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